Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
import queue

h,w = map(int, input().split())

s = [input() for i in range(h)]

white = 0
for i in range(h):
    white += s[i].count('.')

q = queue.Queue()

q.put([0,0])
goal = [h-1,w-1]
visited = [[float('inf') for i in range(w)] for j in range(h)]
visited[0][0]=0

move = [[0,1],[0,-1],[1,0],[-1,0]]

while not q.empty():
    a,b = q.get()
    for y,x in move:
        if 0<=a+y<h and 0<=x+b<w:
            if s[a+y][x+b]=='.' and visited[a+y][x+b]==float('inf'):
                q.put([a+y,x+b])
                visited[a+y][x+b]=visited[a][b]+1

print(white-visited[-1][-1]-1if visited[-1][-1]!=float('inf')else -1)